burning oil!!!

i swapped a dohc zc into my ef9 and i noticed the engine burns alot of oil. i tried using royal purple, castrol synthetic 10-30, 10-40, and now im using 20-50. does anybody know if there is a solution to this? maybe the diff grades of oil will slow it down or if anybody that has tried any additives that actually works. i've tried slick 50 too. it help a little but no much...